This invention relates to a heat pipe thermal transport apparatus and particularly to one having means for reducing the formation of corrosive compounds within the heat pipe.
In general, heat pipes are comprised of a tube having separated evaporator and condensor portions. An external heat source supplies heat to the evaporator portion and a heat sink extracts heat from the condensor portion. Heat pipes are typically sealed and filled with a heat transport fluid medium. During operation, the heat transport medium in a liquid phase is vaporized in the evaporator portion by heat supplied from the external source. The vaporized heat transport medium which contains the latent heat of vaporization flows to the condensor portion of the heat pipe. The vaporous heat transport medium condenses in the condensor portion, thereby giving up its latent heat. Substantially all the internal surfaces of the heat pipe are lined with a wick comprised of a fine porous material. The wick operates to transport the liquid heat transport medium to the evaporator portion by capillary action.
Various working fluids are used as a heat pipe transport medium. One frequently used substance is metallic sodium. During fabrication, the internal cavity of the heat pipe is evacuated and is thereafter charged with the working substance. During charging of the heat pipe, it is virtually impossible to completely remove oxygen from the heat pipe interior cavity. Therefore, after fabrication, some oxygen is present within the heat pipe. When sodium combines with oxygen, highly corrosive sodium oxide is formed. This material can react with the heat pipe housing, which is typically made of a metal, causing it to corrode, thus degrading its structural integrity and heat transfer characteristics. It is, accordingly, an object of the present invention to inhibit the formation of oxides of sodium within the heat pipe interior. It is a further object of this invention to provide this improvement without complicating the heat pipe fabrication process.
In accordance with the present invention, corrosive sodium oxide formation is inhibited through the intentional introduction of substantially pure zirconium into the heat pipe interior. The presence of zirconium causes free oxygen within the heat pipe to react with the zirconium to produce a non-corrosive oxides of zirconium. In accordance with this invention, substantially pure sirconium is introduced into the heat pipe by forming it into long threads which are weaved into a mesh type wick material.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims taken in conjunction with the accompanying drawings.